Conventional techniques for mapping host system memory into virtual machines span a range that runs from simple, one-time actions to complex, dynamic interactions between a host operating system and one or more virtual machines implemented by the host operating system. These conventional techniques include “ballooning,” “hotplugging,” and fixed size configuration. According to ballooning and hotplugging, the host operating system maps physical memory to a virtual machine and dynamically requests that the virtual machine return at least a portion of the mapped memory when needed. Both ballooning and hotplugging require complex and dynamic interactions between the host operating system and a guest operating system executed by the virtual machine. Ballooning additionally requires that the guest operating system include processes configured to execute specialized ballooning logic. Hotplugging requires interactions between the host operating system and the guest operating system to determine when additional memory should be added. This additional memory is conventionally added in large chunks having coarse granularity (e.g., precise to gigabytes or larger units). Moreover, once this additional memory is added, it is difficult to free if the guest operating system's memory usage decreases. According to fixed size configuration, a virtual machine specifies before its creation what its memory requirements are, or a host operating system estimates the virtual machine's memory requirements and maps enough physical memory to meet those requirements. Over-allocation issues are common to fixed sized configuration in which too much memory is allocated to the virtual machine. However, to prevent over allocation, applications to be executed by the virtual machine must pre-register their requirements, which is sometimes infeasible. In addition, conventional host operating system estimates for fixed sized configuration are consistently too small for at least some use cases. Thus, these conventional techniques present potential problems for balancing a whole system because the host operating system has little information or control regarding how one or more guest operating systems implemented by a virtual machine utilize the mapped memory. Thus, using these conventional techniques, physical memory mapped to a virtual machine may be sparsely utilized.